of psychology that were unmeasurable. The James–Lange theory opened the pos-
sibility for an objective assessment of subjective feelings through the measurement
of physiology. Cannon ( 1927 ) rejected this theory, stating that emotions were
created within the brain, centrally—specifically in the thalamus. Cannon critiqued
the James–Lange theory by presenting evidence that chemically induced physio-
logical changes were not sufficient to elicit emotions and that surgery in animals
which disconnected the brain from the body did not prevent emotions from being
expressed in the animals’behavior. According to Cannon, the peripheral physio-
logical changes noted by James and Lange werecoincidentalto, not causative of,
the actual origins of emotions in the brain:“This coincidence of disturbances in
muscles and viscera with thrills, excitements or depressions was naturally mis-
leading, for, with the role of the thalamus omitted from consideration, the obvious
inference was that the peculiar quality of the emotion arose from the peripheral
changes”(Cannon 1927 , p. 120).
Psychologists have used facial expressions—behaviors presumably induced by
the experience of emotions—to identify specific emotions felt by individuals, and
the discovery of cross-cultural similarities in these expressions has been used to
suggest that facial expression and their underlying emotions are universal to our
species (Ekman 1980 ). In the mid-twentieth century, improvements in instrumen-
tation permitted researchers to discover physiological differences associated with
specific emotions; however, these differences were subtle in relation to the overall
physiological arousal (Lang 1994 ). Schachter and Singer ( 1962 ) presented a theory
of emotions that combined elements of peripheral and central causality, in which
perception of arousal or other peripheral physiological changes leads to cognitive
processes in the brain that make sense of the physiological changes, labeling the
situation with an appropriate emotion. Thus, Schachter and Singer’s theory
emphasizes the general nature of the physiological response; this two-factor theory
of emotions requires both a physiological state of arousal and a cognitive process
that categorizes the arousal. The cognitive labeling is based upon both individual
experience and cultural background, and it arises from an attempt to understand the
meaning of the physiological activation. For example, an individual experiencing
intense activation upon seeing another person smile might interpret the emotion as
affection, while the exact same physiological activation when seeing the other
person scowl might lead to an interpretation that the emotion is fear.
Experiments by Mandler and coworkers found very little correlation between
physiological measures of stress and self-reports of feeling anxious (Mandler and
Kremen 1958 ; Mandler et al. 1958 , 1961 ). However, spontaneous verbal behavior
indicative of emotion was more closely related to the physiological measures,
suggesting that thereportingof feelings is where the major discordance occurred.
A study carried out by Lang et al. ( 1993 ) showed that, on average, reported
emotions upon viewing evocative photographs were correlated with physiological
responses, but that there was much individual variability in the relationship between
physiology and report. This is supported by the great inter-individual variation
documented for how accurately people are capable of monitoring their
4 D.E. Brown and L.L. Sievert